In the formation of integrated circuits, devices such as transistors are formed at the surface of a semiconductor substrate in a wafer. An interconnect structure is then formed over the integrated circuit devices. A metal pad is formed over, and is electrically coupled to, the interconnect structure. A passivation layer and a first polymer layer are formed over the metal pad, with the metal pad exposed through the openings in the passivation layer and the first polymer layer.
Post-passivation interconnect (PPI) is then formed to connect to the top surface of the metal pad, followed by the formation of a second polymer layer over the PPI. An Under-Bump-Metallurgy (UBM) is formed extending into an opening in the second polymer layer, wherein the UBM is electrically connected to the PPI. A solder ball is then placed over the UBM and reflowed.